Hemophilia A is a hereditary bleeding disorder caused by a lack of blood clotting factor VIII.

Causes, incidence, and risk factors:

Hemophilia A results from a deficiency (lack) of clotting factor VIII.

The disorder is caused by an inherited X-linked recessive trait, with the defective gene located on the X chromosome. Females have two copies of the X chromosome, so if the factor VIII gene on one chromosome doesn't work, the gene on the other chromosome can do the job of making enough factor VIII. Males, however, have only one X chromosome, so if the factor VIII gene on that chromosome is broken, they will have hemophilia A. Thus, most people with hemophilia A are male.

If a woman has a defective factor VIII gene, she is considered a carrier. This means the defective gene can be passed down to her children. In a woman who carries the defective gene, any of her male children will have a 50% chance of having hemophilia A, while any of her female children will have a 50% chance of being a carrier. All female children of men with hemophilia carry the defective gene. Genetic testing is available for concerned parents.

The severity of symptoms can vary. Severe forms become apparent early on. Bleeding is the main symptom of the disease and sometimes, though not always, occurs if an infant is circumcised. Additional bleeding problems are seen when the infant starts crawling and walking.

Mild cases may go unnoticed until later in life when they occur in response to surgery or trauma. Internal bleeding may happen anywhere, and bleeding into joints is common. Risk factors are a family history of bleeding and being male.

Rarely, adults can develop a bleeding disorder similar to hemophilia A. This may happen after giving birth (postpartum), in people with certain autoimmune diseases such as rheumatoid arthritis, in people with certain types of cancer (most commonly lymphomas and leukemias), and also for unknown reasons (called "idiopathic"). Although these situations are rare, they can be associated with serious, even life-threatening bleeding.

Many blood clotting tests are performed if the person tested is the first one in the family to have a bleeding disorder. Once the defect has been identified, other family members will need less testing to diagnose the disorder.

Standard treatment involves replacing the missing clotting factor. The amount of factor VIII concentrates needed depends on how severe the bleeding is, the site of the bleeding, and the size of the patient.

Mild hemophilia may be treated with desmopressin (DDAVP), which helps the body release factor VIII that is stored within the lining of blood vessels.

To prevent a bleeding crisis, people with hemophilia and their families can be taught to give factor VIII concentrates at home at the first signs of bleeding. People with severe forms of the disease may need regular preventative treatment.

Depending on the severity of the disease, DDAVP or factor VIII concentrate may be given before having dental extractions and surgery to prevent bleeding.

Immunization with hepatitis B vaccine is necessary because of the increased risk of exposure to hepatitis due to frequent blood infusions.

Patients who develop an inhibitor to factor VIII may require treatment with other clotting factors such as factor VIIa, which can help with clotting even without any factor VIII.

Support Groups:

For additional resources, see hemophilia support group.

Expectations (prognosis):

With treatment, the outcome is good. Most people with hemophilia are able to lead relatively normal lives. A small percentage of people with hemophilia will develop inhibitors of factor VIII, and may die from loss of blood.

People with hemophilia A should establish regular care with a hematologist (blood doctor), especially a doctor who is associated with a hemophilia treatment center. The ability to have quick and easy access to medical records documenting the level of factor VIII that the person has had, the history of factor transfusions (including the types and amounts), any complications, and the type and amount of any inhibitors can be lifesaving in the event the person with hemophilia is in an emergency situation.

Complications:

Chronic joint deformities, caused by recurrent bleeding into the joint, may be managed by an orthopedic specialist. These problems sometimes require joint replacement.

Recurrent transfusions may increase the risk of contracting HIV and hepatitis . Since 1985, however, blood screening procedures were improved for detecting the HIV virus. And new heat processing treatment makes factor VIII material free of the HIV virus and thus safe for use.